Recently, the application range of magnetic recording devices such as magnetic disk devices, flexible disk devices, and magnetic tape devices has been markedly increased, the importance of the magnetic recording devices has increased, and the recording density of a magnetic recording medium used in such devices has shown a corresponding marked improvement. Particularly, since the introduction of MR heads, PRML techniques, and the like, the surface recording density of an HDD (hard disk drive) has been intensively increased, and recently, a GMR head, a TuMR head, and the like have been introduced, and accordingly, the surface recording density continues to increase at the pace of about 1.5 times per year.
Meanwhile, as a magnetic recording type of an HDD, recently, a so-called vertical magnetic recording type has come into widespread use as a technique replacing the conventional in-plane magnetic recording type (a recording type in which the magnetization direction is parallel to the substrate face). In such a vertical magnetic recording type, crystal particles included in a recording layer, in which information is recorded, have an axis of easy magnetization in a direction vertical to the substrate. The axis of easy magnetization represents a direction in which the magnetization is easily oriented, and, in the case of a Co alloy that is generally used, is an axis (c axis) that is parallel to the normal line of plane (0001) of the hcp structure of Co. According to the vertical magnetic recording type, since the axis of easy magnetization of magnetic crystal particles is in the vertical direction, there are characteristics such that, even when the implementation of a high recording density progresses, the effect of the diamagnetic field is small between recording bits, and static-magnetic stability is achieved.
For the vertical magnetic recording medium, generally, film formation is performed in the order of a base layer, an intermediate layer (alignment control layer), a recording magnetic layer, and a protection layer on a nonmagnetic substrate. In addition, there are many cases in which after film formation up to the protection layer is performed, a lubricating film is formed, with which the surface is coated. Furthermore, in many cases, a magnetic layer called a soft magnetic backing layer is disposed under the base layer. The base layer and the intermediate layer are formed for the purpose of further improving the characteristics of the recording magnetic layer. More specifically, the base layer and the intermediate layer have a function of controlling the form of the magnetic crystals while at the same time arranging the crystal alignment of the recording magnetic layer.
The above-described magnetic recording medium is configured by laminating a plurality of thin films that are formed mainly by using a sputtering method. Accordingly, the magnetic recording medium, generally, is manufactured using an in-line type film-forming apparatus in which a plurality of chambers (processing devices) forming thin films configuring the magnetic recording medium is connected in one row through a gate valve. Here, each chamber is configured to include a reaction vessel including a pair of electrodes, a gas-introducing tube that introduces gas into the inside of the reaction vessel, a vacuum pump that discharges gas placed inside the reaction vessel, and the like. In such an in-line type film-forming apparatus, a substrate as a processing target is sequentially conveyed to the inside of each chamber, and a predetermined thin film is formed inside each chamber. Accordingly, in the in-line type film-forming apparatus, by passing the substrate in one cycle, thin films corresponding to the number of chambers can be formed on the substrate (for example, see Patent Document 1).
However, as an example of the problem that occurs most frequently when a magnetic recording medium is manufactured using such an in-line type film-forming apparatus, there is the dropping of a processing target substrate from a carrier that holds the processing target substrate inside the reaction vessel. More specifically, in the in-line type film-forming apparatus, processes such as film formation and the like are performed for a processing target substrate while a holder that maintains the processing target substrate sequentially conveys an installed carrier between a plurality of chambers, and there is a case where the processing target substrate falls from the carrier in the middle of the conveying process so as to stop the device.
More specifically, a carrier used in a conventional in-line type film-forming apparatus, for example, as illustrated in FIG. 13, has a structure in which holders 301 are installed to the upper portion of a support base 300. The holder 301 includes a hole portion 302 that arranges the processing target substrate W′ on the inner side thereof and a plurality of supporting arms 303 that are disposed so as to be elastically transformable on the periphery of the hole portion 302 and can hold the substrate W′ inserted into the inside of each supporting arm 303 to be detachably attached while the outer peripheral portion of the processing target substrate W′ is brought into contact with the plurality of supporting arms 303.
Here, when the magnetic recording medium is manufactured, the temperature of the carrier slowly rises due to an electric discharge or heating occurring inside the chamber and is finally 250° C. or more. At this time, a supporting position between the supporting arm 303 and the processing target substrate W′ in the above-described holder 301 is displaced by about 1 mm due to thermal expansion of the carrier. In the in-line type film-forming apparatus, in a case where such a displacement occurs, there is a case where the processing target substrate W′ is dropped out of the holder 301 when the substrate W′ is detached from the holder 301 by a robot.
Accordingly, in a conventional in-line type film-forming apparatus, although the handling position is adjusted by estimating the deformation due to such thermal expansion, the deviation at the handling position needs to be suppressed to about 0.1 mm, whereby an operator's skill is necessary. In other words, it is necessary for an operator to perform positional adjustment while the above-described displacement is predicted, and monitoring needs to be continued while an increase in the temperature of the carrier is waited for even after the positional adjustment.
In addition, in manufacturing the magnetic recording medium using the in-line type film-forming apparatus, in order to increase the production capacity, it is demanded that the carrier be light-weight, and the conveying speed of the carrier be increased.
In the in-line type film-forming apparatus, in a case where the above-described trouble of the dropping of the substrate from the carrier occurs, first, the reaction vessel is open after the inside of the reaction vessel is formed to be in the state of atmospheric pressure, after the fallen substrate is taken out from reaction vessel, the inside of the reaction vessel is decompressed again, and then the device is restarted. Here, while the operation of removing the substrate from the reaction vessel is completed in several minutes, a time of several hours is needed until the device is restarted thereafter by decompressing the reaction vessel, and accordingly, there is a problem in that the productivity of the magnetic recording medium decreases. Particularly, since higher crystallinity is required for thin films configuring the magnetic recording medium, it is necessary to set base pressure (the degree of vacuum reaching the maximum) as a higher-vacuum side and to perform film formation in an environment in which the amount of impurity is small. Accordingly, a time required for decompressing the reaction vessel essentially increases.